Abstract: This invention relates to a new supported catalyst and to the use of this catalyst in a process for the polymerization of alpha-olefins. The catalyst comprises a transition metal complex supported on a planar organosilicon polymer which has been derived from at least one of chrysotile and apophyllite. The support is prepared by the leaching of the metal ions from the mineral and substitution of some of the silanol groups with alkyl silyl groups. Particularly active catalysts can be prepared by treating the planar organosilicon polymer with silicon tetrachloride prior to contacting the polymer with a transition metal complex.